The Weapons Systems & Platforms (WP) Program Area often issues SERDP Exploratory Development (SEED) Statements of Need (SONs) calling for proof of concept research to address environmental concerns for the Department of Defense (DoD). In 2012, WP released a Fiscal Year (FY) 2014 SEED SON calling for research on environmentally sustainable binder systems for energetic materials. For several decades, DoD has relied on cast cure binder systems, which contain diisocyanate, for the production of energetic formulations. Diisocyanate has well known Environmental, Safety, and Occupational Health (ESOH) risks ranging from skin irritation to carcinogenic and reproductive effects. Other materials with ESOH risks, such as phthalates, may also be commonly used in energetic binder formulations. The European Union Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) Organization has listed several of these materials on their Authorization List. To address the potential for further regulation in the U.S. that may limit or restrict material availability, DoD is pursuing research to develop novel binder systems that do not utilize diisocyanates, phthalates, or other chemical compounds with ESOH issues.
Two SEED projects selected to pursue research on this topic have shown significant progress. Under project WP-2406, Dr. Andrew Guenthner and his team at the Air Force Research Laboratory have developed isocyanate-free solid rocket motor propellant binders that are inspired by natural reactions found in plants and animals. The feasibility of this material to serve as an environmentally friendly alternative to isocyanates in solid rocket propellant has shown promising results throughout project research. This simplified one-step modification of commercially available polymer performs comparably with isocyanate-cured systems. The benefits of utilizing the resultant binder system will be more thoroughly realized with continued development of the technology. Dr. Guenthner’s project was previously highlighted as part of SERDP and ESTCP’s Webinar Series.
For project WP-2407, Dr. Pascal Dubé and his project team at Nalas Engineering, Inc. and the Naval Air Warfare Center Weapons China Lake Division, developed a new technology for binders relying on the ligation of neutral components that are well-known for their compatibility with living organisms, and use as probes in living cells and animals without disrupting biological functions. The binder developed in this effort showed compatibility with energetic materials and common formulation ingredients while offering promising physical properties upon reaction. Moreover, upon further testing the new system could be directly integrated into current formulations with no or minimal change from the formulator’s perspective.
Both of these SEED projects have developed a viable proof of concept for alternatives to isocyanate-based formulations for propellants, and anticipate submitting proposals for continuation of work under the scope of a SERDP Core project. SERDP aims to continue producing successful SEED efforts, and recently released the FY17 Core and SEED SONs.